Sturdy high-torque crank handle for PLTW automata and Vex robotics

I reworked my earlier crank handle when I found that the students were still breaking the barrel off the stem (the Teenager Test). This one is best printed with three vertical shells, with the parts in the orientation I have shown in the pictures. I use a little bit of support under the stem, nothing special, just let the program generate it. The barrel and stem are print in place--the barrel should easily break free. It is loose and turns freely.

I have been able to just press-fit the parts together with some filaments. With others, it's been necessary to do a minimal amount of trimming on the peg end of the stem in order to seat it. If your parts are loose, use a little CA glue to secure them. I have not needed to do this-the tolerances are tight! This handle can withstand having its parts pressed together in a bench vise, just go slowly.

This crank is strong enough to run two brass axles running six cams, linked by a timing belt that is driven by metal gears with tensioners. I had started with wooden axles, which broke under the stress, but the handle never did. It's my new go-to.

The handle will work fine for Vex robotics parts too. I have included the 3mf file for a version of the handle with a square hole for Vex axles. So far so good, the first-year students are not breaking them.

The model in the pic was made of Jessie PLA. I've made these in ASA and PETg as well, and they are all fine.